21277665 has 12 divisors (see below), whose sum is σ = 36881364. Its totient is φ = 11348064.

The previous prime is 21277657. The next prime is 21277667. The reversal of 21277665 is 56677212.

It can be written as a sum of positive squares in 2 ways, for example, as 9437184 + 11840481 = 3072^2 + 3441^2 .

It is not a de Polignac number, because 21277665 - 2³ = 21277657 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21277667) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 236374 + ... + 236463.

It is an arithmetic number, because the mean of its divisors is an integer number (3073447).

Almost surely, 2^21277665 is an apocalyptic number.

It is an amenable number.

21277665 is a deficient number, since it is larger than the sum of its proper divisors (15603699).

21277665 is a wasteful number, since it uses less digits than its factorization.

21277665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 472848 (or 472845 counting only the distinct ones).

The product of its digits is 35280, while the sum is 36.

The square root of 21277665 is about 4612.7719432029. The cubic root of 21277665 is about 277.1030604355.

It can be divided in two parts, 212 and 77665, that added together give a palindrome (77877).

The spelling of 21277665 in words is "twenty-one million, two hundred seventy-seven thousand, six hundred sixty-five".